The present invention relates to the field of semiconductor manufacturing; more specifically, it relates to a method of protecting the backside surface of semiconductor substrates.
In the manufacture of semiconductor devices, semiconductor substrates, most notably, silicon wafers, are subjected a wide variety of process steps during formation of devices on the frontside of the substrate. These process steps include forming process films, etching process films, etching the substrate itself and placing dopants into the substrate to name a few. During these processes, it is important to protect and/or seal the backside of the substrate from damage or contamination. For example, mechanical damage to the backside or formation of rails on the backside during frontside only film formation can affect photolithographic processes, the backside of the substrate can become contaminated and then contaminate the frontside of the adjacent substrate or backside charging can occur, leading to defective or inoperable devices.
With many traditional film formation tools, process films are formed on the backside of the substrate as a by-product to frontside film formation. These incidentally formed backside films are used to protect or seal the backside of the substrate.
With the advent of frontside only deposition tools such as those used in high-density plasma (HDP) and rapid thermal chemical vapor deposition (RTCVD) tools, incidental backside films are no longer available to protect and/or seal the backside of the substrate. The lack of incidental protective films will create a series of undesirable effects including: inability to remove some process films formed on the backside, inability to prevent or remove backside defects, inability to minimize charging events at subsequent processing steps, attack of the backside of the substrate or backside process films during backside rail removal, and contamination of the backside of the substrate.
Therefore, there is a need to provide purposefully formed backside films at strategic steps in the fabrication processes in order to avoid the undesirable effects cause by the lack of incidental backside films.
A first aspect of the present invention is a method of fabricating a semiconductor device, comprising: (a) providing a bare semiconductor substrate, the substrate having a frontside and a backside; (b) forming one or more protective films on the backside of the substrate; and (c) performing one or more wafer fabrication steps.
A second aspect of the present invention is method of fabricating a semiconductor device, comprising: (a) providing a bare semiconductor substrate, the substrate having a frontside and a backside; (b) forming a protective film on the frontside and the backside of the substrate; (c) removing the protective film from the frontside of the substrate; and (d) performing one or more wafer fabrication steps.
A third aspect of the present invention is method of fabricating a semiconductor device, comprising: (a) providing a bare semiconductor substrate, the substrate having a frontside and a backside; (b) forming a first protective film on the frontside and the backside of the substrate; (c) forming a second protective film over the first protective film; (d) removing the first and second protective films from the frontside of the substrate; and (e) performing one or more wafer fabrication steps.